Electric circuit



Oct. A22, 1940. J R HFELE v2,218,709

ELECTRIC CIRCUIT Filed May 19,l 1939 Ls'wsep if 45 CMENSR 50 ATTORNEY flis- Patented Oct. 22,. y

y Telephone Laboratories, Incorporated,J NewV n Yo rkN.v Y.`a. 'corporation 'of Newv York if iThis invention relates Ito electric condenser vcharging and discharging circuits and morespe`V ycic'ally to sweep circuits suitable for television scanning...

" rIn vthe operation of cathode raytubes suitable i for television scanning, thesweep vcircuitsy used ,y have beengenerally of `a form'in which there is 4an' unbalance, i. e., the instantaneous average of. thepotentials toground generated by the lsweep circuit and applied to Vthe deflecting platesirof a cathode ray tube does notsubstantially equal the. potential to .ground of #the .acceleratingxanode "cathode ray tube at 'all times. It 'has' -jbeen found that this vis the cause of the eld .onthe screen onthe cathode rayt'ubefbeing somewhat wedge- Shaped and so producing a' distorted image,.fthe reason therefor being that the velocity of the applied towthe sweep-plate; and 'hence the dee ection in certain beam positions when this aver'- age isnot substantially constant isgreater'or This'unbalance also ac'.

, less thanit should be.

counts for an unwanted intensitydeviation and 2.5 a loss of clear focus in parts oflthe image.` 'I'hese three manifestations arealldue vto the change in velocity of thebeam. Various'arrangements o have heretofore been :suggested f r"proc`lucing` L ,balanced swe'e'ppotentials'. "The present-'invem' tion is directed to'improvements in that type of but in certain of [its aspects is not limited to'this use, as will be apparent' from thefollowing de-y gscrption and the appended claivms.-

.chosen by way of illustrationftwo `condensers are provided which are 4arranged Ain s eresrela- K tionship in thecircuit to whichjthey supply voltage,y one of these condensersI being charged under control of the other and ,substantially simultaneously therewith, both condensers thenbeing discharged together in series to setup a voltage equal at alltimes to the sum of the'voltages across thev respective condensers., The common tere at a lixed potential when Ithe arrangement .is used to generate sweep voltages for a cathode ray.

f In/one specific embodiment hereinafter described;v two high vacuum electron discharge devices have.

their.' respective input and output circuits inter connected so as to produce 'sharp output pulses fonperiodically and quickly `:l ia`.rging the joneof condensers whichcontrols the charging.I of f theother. This control is effected by means of an electrondischarge tube rhaving the controlling immediately preceding the deflecting 'plates intheV beamv depends upon4 the averageof the potentials circuit which produces balancedv sweep potentials vIn the embodiments of the V`inventionl hereinl minal of the condensers is'preferably maintained" condenser in its input circuit andjitsjcontrolled condenser in the' output circuit thereofsL-,c Ay pentode tube isprovidedffor discharging bothpf the condensers" linearly: with 'respect'ft'otir'nec' Thesecond condenserv has .producedracrossit 'al saw-'toothed wave which is 180 degreeslfout 'off phase with rrespect tov thatV across' the iirstcone' denser,I giving a voltage outputacross .the icondensersy which is balanced withrespect to `thepo; tential of their 'common terminal; V'Ihe Vexternal terminals of the condensersareva'pplied through` coupling condensers to-the respective .plates or. one set of deflecting platesr of a 'cathode ray tube.

Acrossthese deecting plates isconnec'ted ay high resistance', the mid-point` of which is connected toV an fano'de 'o f the cathode 'ray tube-adjacent thedeflecting plates. This arrangementjproduce's a potential wave 'of the well-known saw-,tooth waveform which is substantially .balanced with respect'to the potential vapplied to this anode;y

. 'Ina second embodimentgthe pulses for charg.-

` ling the'condensers areproduced in a'separate gas-"4 `filled tube, thus eliminating'vthe' necessity for 'the tronv discharge devices which' were interconnected' in theembodiment described. above. 1 The invention will be more readilyunderstoo from *the following descriptionl taken in connec-v I tiony with thel accompanying drawing forming a part'the'reof in which:

'n Fig. 1 shows a. circuit for producing balanced rsweep potentialsin accordancefwith theinve1i` tion;y 'Y l.

' Fig. 2 shows the shape of thepulsesirnpressed on .the grid of theftubeused'for. charging the sweep condensers; and y j Fig. 3 showsa modicationfof thejcircuitof .Referring'more particularly to 1th`earrang e ment shown in Fig.` 1 offthe drawinga sweep cirf 4of saw-tooth wave form for application ,to the 2 deflectingplates of a cathode ray tube to cause,"

in cooperation .with another sweep circuit of ap-r propriate frequency'. a cathode ray. beam gene- A ated therein to scan in turnv all-of the elemental areas of aiield of viewo'ff'a screen ortarget.

The 'circuit comprisesftwo substantially equal condensers-EI lj and I 2 connected' in series, they common `terminal I3 'of which'is connected 'tofa @fixed potentialas, for-example, grolflnd.,"N'Ih'ey term?fcondenser4 asused` .in this speciiipation'is v cuit is provided for producing balanced potentials lconsidered to'be broadenough to'describe the u electrical action of. -anyftwo` conductors serw-l l' arat'ed'by'a dielectric. Shunted across 'the con'-r densers II and I2 is a suitable constant current device I4. This constant current device may be a saturated diode but it is preferably a pentode electron discharge device I4 having an anode I5, a cathode i5, a control grid I1, a screen grid I3 and a suppressor grid I9. Due to the extended linear portion of the anode voltage versus anode current characteristic of the pentode tube, the condensers I I and I2 are discharged substantially linearly with respect to time through the oonstant current device I4. Thefcontrol grid I1 of the pentode I4 is adjustably biased with respect to the cathode I6 by means of a source of potential 20 which is shunted by a voltage dividing resistance 2I from which adjustableconnection is made to the grid I1. The screen grid I8 is positively biased with respect to the potential of the cathode I6 by means of the source of 'potential 22. 'Ihe suppressor grid I9 is preferably placed at the same potential as that of the cathode I 6.

In order to suddenly charge the condensers II and` I2 periodically and substantially simultaneously, a vacuum tube arrangement comprising tubes A, Band C is employed'. Tube A preferably comprises an anode-23, a cathode 24, a control grid 25,v `a, screen grid 2E and a suppressor grid 21. The tube B preferably comprises an anode, 28, a` cathode 29 and a control grid 30, While the tube C preferably comprises an anode 3I, a cathode 32 `and' a control grid 33. Each of the tubes A, B and C is preferably a high vacuum tube as is also, of course, the constant current device I4.

lIncluded between the cathode 24 and the control grid 25 of the tube A is a'potentiometer resistance 34 and a current limiting resistance 35. The screen grid 26 is preferably biased positively with respect to the cathode 24 vby means of the source 36. The suppressor grid 21 is preferably connected directly to the cathode 24.

Asource of synchronizing waves or impulses S is applied across the potentiometer resistance 34. This source S may be located at the transmitter or at the receiver and may take any of a number of well-known forms. In the preferred embodiment, however, thesource S may comprise a vacuum tub-e oscillator for generating'sine waves of scanning or framing frequency. If the circuit now being described is used. in connection with a cathode ray tube at a receiving station, the frequency and phase of the. source S will be synchronized with theV scanning at the transmitting station by any well-known means.

Included in a circuit between the anode 23.' and the 'cathode 24 of the tube A is an anode resistance. 31 and aI source of potential 38. The anode 23 is connected directly to the grid 3'9 of the tube B. Included in a circuit between the anode 28 and the cathode 29 of the tube B is a resistance 39, a source of potential 49 and the sweep condenser Il. The anode 28 is connected back to the control grid 25 of theV tube A through a coupling condenser 4I.

'The terminal X of the sweep condenser II (the terminal not at ground potential)` is connected through a coupling condenser 42 to the grid 33 of the tube C. Included in the circuit between the grid 33 `and the4 cathode 32 of the tube C is a biasing source of potential 43 and a resistor 44. Included in the circuit between the anode 3l and the cathode 32 of the tube C is an anode resistance 45, sweep condenser I2 and a source of `anode potential 4E.

The changing potential across thesweep con.- densers II and I2 is applied to a pair ofelectro'- cuit which charges the sweep condenser static defiecting plates 41 and 48 arranged in a cathode ray tube T of any suitable design in which balanced electrostatic deflection is used, a portion only of the tube T being shown. As an example of a satisfactory cathode ray tube for this purpose, reference may be made to an application of C. J. Davisson, Serial No. 118,277, l-ed December 30, 1936. A pair of coupling condensers 49 and 50 is utilized between the sweep condensers I I and I2 and the deflecting plates 41 and 48. Connected across the delecting plates 41 and 48 is a high resistance 5I, of the order of several megohms, the mid-point 52 of which is connected to anv anode 53. By this arrangement the potentials applied to the deflecting plates are at all times balancedv with respect to the potential of the anode member 53 which may be any anode in the cathode ray tubeabout whose potential it is desired to balance the potentials applied to the deflecting plates. If desired, the potentials of the sweep plates may be balanced `with respect to a fixed potential which is not the'exact potential of any of the velectrodes in the tube, in which event; the deflecting plates serv-e as an electron lens member in additon to a deflecting means.

The circuit shown in Fig. l operates as follows: A synchronizing voltage is fed to the grid 25 of the tube A from the source S through the potentiometer 3'4. 'I'he steady grid potential of tube A caused by the current flowing in .the gridcathode circuit is adjusted to nearly zero with respect to the cathode 24 by making the resistance 35 high (of the order of 50,000 ohms). The amplitude of the synchronizing voltage is such that during the negative portion of the cycle, the grid potential is swung so far negative that the current flow ceases in the anode-cathode circuit. The anode 23 is then at the potential of the positive terminal of the anode source 38, which potential is positve with respect to ground. The grid 30 of the tube B is also at this potential. The cathode 29 of the tube B has been approaching ground potential ata rate determined by the discharge circuit of the sweep condenser II including the constant current tube I4. This` rate is so adjusted that at the time when the grid of the tube B is suddenly made positive with respect to ground, the cathode 29' of the tube B is not very far from ground potential.` A large current then flows from the source of potential 40 through the resistor 39` and tube B to suddenly charge up the condenser II so that the potential of the point X is highlypositive with respect to ground. This initial large current produces a potential drop across' the resistor 39 which is transmitted as a pulse through the coupling condenser 4! to the grid 25 of the tube A. This pulse tends to hold the ytube A inits cut-off condition until current has ceased to flow through the resistor 39 to the sweepv condenser I'I, which occurs when condenser I I is charged to its maximum potential.

v 'Ihis initially large charging pulse on the condenser II is transmitted likewise through the capacity 42 to the grid 33 of the tube C. This tube has been prevented from conducting current by a steady large negative grid potential applied from the source 43 through the resistor 44; A large charging pulse-positive in direction-- starts current flowing in the cathode-anode cir- I2 so that point Y reaches a maximum negative potential with respect to ground. Tubes B and C then become inoperative since in each of them, the cathode and the anode are almost at the same sweep wave or" 5,760 cycles.

In a specific instance where the arrangement described above was satisfactorily operated, the` resistance 35 was 50,000 ohms, the resistance 31 was 500,000 ohms, the resistance 39 was 2,000 ohms, the resistance M was 100,000 ohms, the resistance l5 was 2,000 ohms and the resistance 51 was 10 to 2,0 megohms, the condenser 4| was .0001 microfarad, the condenser 42 was .0001 microfarad and each of the condensers I l and l2 was .00025 microiarad, this circuit producing a In the arrangement for 24 cycles the condensers ll and l2 were each ofj .02 microfarad capacity and certain of the other circuit elements were correspondingly changed.

Various modiiications may obviously be made without departingr from the spirit of the invention, the scope of which is dened by the appended claims.

What is claimed is:

1. A wave generator comprising a condenser, means for charging said condenser, a second condenser, means for charging said second condenser duringsubstantially all the charging time of said rst condenser comprising means responsive to the Voltage across said rst condenser due to the charge built up thereon, and means for discharging said condensers together in series so as to set up a voltage equal at all times to the sum of the voltages across said respective condensers,

2. A wave generator comprising a condenser, means for charging said condenser, a second condenser, means for charging said second condenser during substantially all the charging time of said rst condenser comprising means responsive to the voltage across said first condenser due to the charge built up thereon, means for continuously maintaining one terminal of each condenser at the same fixed potential, and means for discharging said condensers together in series so as to set up a voltage equal at all times to the sum of the voltages across said respective condensers.

3. A saw-tooth wave generator comprising a condenser, means for quickly charging said condenser, a second condenser, means for charging said second condenser during substantially all the charging time of said rst condenser com, prising means responsive to the voltage across said first condenser due to the charge built up thereon, and means for relatively slowly discharging said condensers together in series at a substantially constant rate so as to set up a voltage equal at all times to the sum of the voltages across said respective condensers,

4. In a Wave generator, a pair of condensers having a common terminal which is connected to a point of fixed potential and each having an outside terminal, means for charging one of said condensers, means responsive to the potential across said rst condenser for substantially simultaneously charging the other of said condensers, and means for discharging the two condensers together, whereby a saw-toothed potential wave is produced between said outside terminals, which potential wave is balanced with respect to said point of xed potential.

5. In combination, a condenser, a second condenser, each of said condensers having a terminal which is placed at a common fixed potential, and means for varying the charges on said condensers substantially simultaneously, said means comprising mechanism for varying the charge on one condenser in one direction, means responsive to thez voltage due to said variation in charge for Varying the charge on said second condenser in the same direction, and a single electron discharge device for simultaneously varying the charge on said condensers in the opposite direction.

6. In combination, a condenser, a second condenser, each of said condensers having a terminal which is placed at a common xed potential, means for quickly and substantially simultaneously charging said condensers, said means comprising mechanism for charging one condenser, and means responsive to the voltage across said first condenser due to said charge for charging said second condenser, and means for discharging said condensers.

7. In combination, a condenser, a second condenser, each of said condensers having a terminal which is placed at a common iiXed potential, means for quickly and substantially simultaneously charging said condensers, said means comprising mechanism for charging one of said condensers, and means responsive to the voltage across said first condenser due to the charge built up thereon for charging said second condenser substantially simultaneously therewith, and means including a constant current device for discharging said condensers simultaneously and substantially linearly with respect to time.

8. In combination, a first condenser, a second condenser, each of said condensers having a terminalY which is placed at a common xed potential, high vacuum means for quickly varying the charge on said rst condenser in one direction, and a high vacuum electron discharge device coupled to said high vacuum means and responsive thereto for quickly varying the charge on said second condenser in the same direction substantially simultaneously with the variation in charge on said' first condenser.

9. In combination, two substantially equal condensers, means for connecting one terminal of each condenser to a terminal of the other condenser, means for connecting this common terminal to a point of xed potential, a high vacuum electron discharge device having input and output circuits, a second high vacuum electron discharge device having input and output circuits, means for applying signals to the input circuit of said first electron discharge device, means for connecting the output circuit of said rst electron discharge device to the input circuit of said second electron discharge device, means for connecting said first condenser in the output circuit of said second electron discharge device, a third high vacuum electron discharge device having input and output circuits, means for connecting the input circuit of' said third electron discharge device to the output circuit of said second electron discharge device, and means for connecting said second condenser in the output circuit of said third electron discharge device, whereby said condensers are charged substantially simultaneously upon the appearance of a signal in the input circuit of said rst electron discharge device.

10. In combination, two substantially equal condensers, means for connecting one terminal of each condenser to a terminal of the other condenser, means for connecting this common terminal to a point of xed potential, a high vacuum electron discharge device having input and output circuits, a second high vacuum electron discharge device having input and output Qrcuits. mcar1s ier applying signals to the input circuit yof, said electron discharge device,` v means' for*connectingl theoutput circuit ,ofjsaid irst :electron discharge device to the input circuitl of4 said second electron discharge device, means Yfor connecting lsaidfiirst condenser in the output circuit of 'said secondA electron discharge device, means for vvfeeding back. energyfrom the output o ffsaid second electron discharge device to the' l ,f Vinputcircuit.of saidffirst electron'v discharge device, 'phase inverting means, and means for connecting .SaidI second .condenser in the output ,cir-

cuit of said ,electron discharge devicev through Y s aidphase inverting 4 means whereby the charge dnfthev first condenservariessubstantially simul- 5 denser, means for connecting this common terminaljto 'a point of y fixed'p'otential, a high vacuum v`ele'ctrr'i Idischarge device havinginput and Voutput circuits, a second'high vacuum Lelectron discharge devicehaving inputand output circuits, means vfo'rjapplying pulses tothe input` circuit of said firstfelectron discharge 'devicameans for connectling the voutputcircuit yoffsaid `first electron discharge device to fthe input circuit vof'said second electron discharge y`devi`ce,.means for connecting. sa'idflrst cc'infcleriserv in the output circuit of said second electron discharge device, a third electron 1 y discharge device having input and output circuits,

' thefoutputjcircuit of said third electron discharge `e,,whereby said condensers are charged sub-I 'means for conne'ctingj'the input.l circuit of said third electron discharge device to' thefoutput cir- 5.

cuit cf said second electron discharge device,

` meansfforl' conilecting said. ,second condenser,` in

stantiallysimultaneously upon the appearance of a; pulse in they input' circuit vvof said first' electron;

, discharge device,and means including a constant current device forldischarging said condensers substantially linearly vwith respect to time between pulses..

lav-,In combination, ya iirst condenser, a second condenser, ineans'for placing a terminal of each i of said condensers at the same iixed potential, and means for charging said condensers quickly and substantially simultaneouslycomprising a rst.

high vacuum'electron discharge device having an `anodea cathode and a grid, a second high vacuum electron discharge device havingl an anode,

a cathode and a grid, and a third electron discharge device havingv an anode,` a cathode and a grid, means for connecting a source of signals between said cathode and grid of said rst electron discharge device, means for connecting theanode of said rst electron discharge device to the y grid of said second electron discharge device, means for connecting said rstfcondenser in circuit between said anode and saidcathode of said second electron discharge device, means for f' connecting the cathode of said first electron discharge device to said point of xed'potential,

means for connecting said cathode of said second electron discharge device to the grid of said' third electron discharge device, means for connectingthe cathode of said third electrondischarge device through asource of potential to said'point of fixed potential, and means for connecting the anode of said third electron discharge device through said second condenserto said point of xed potential. y 13. In combination, a iirst condenser, a second condenser, means for placing a terminal of each discharge device'having anl anode, a cathode and anode of said yiirst electron discharge devicetc'r1` Agrid of said first electron discharge device.-

of said condensers at the same iixed potential;`

' and means for chargingsaidcondensers quickly' and substantially simultaneously comprising'a rst high vacuum electron discharge device hav-'f ing an anode, a cathode andag'rid,v asecond high vacuum electron discharge devicer having f an anode, a cathode and a grid,`and a'third electron discharge deviceA having an anode, a cathode 'and V"a grid, means for'fconnectinga source of signals between said cathodeandgrid of said iirst electron discharge device, "means for yconnecting the anode ofl said rst electron,

Vdischarge, device to the grid of said secondelle'c tron discharge device, vmeansfor ccnnecting'saidL iirst condenser in circuit between said anode and', 115 Y said cathode ofsaidsecond electronjdiscl:large;l l' device, means for connectingthe anodel o f. said second electron dischargey device to the' gridlfoff said first electron discharge device, meansfior, 20'

connecting the cathode of said second electron discharge device to the grid'of `said Ithird., electron discharge devicefand means for connectingi the second condenser in circuit between.",sa 'i`d` anode. and said cathode of said thirdl electron, ,i7 I 25 discharge device, t n

14. In combination, a first condenser,` `a second.7

condenser, means for placing a terminal .of each of said `condensers at the Asame ,fixed potential;`

means for charging said condensersquicklyand 5,

substantially simultaneously comprising a" lrst. highgvacuum electron discharge devicehaving.- an7 anode, a` cathode fand a grid, a secondhi'gh' vacuum ,electron discharge device having f anfa'n! ode, a cathode and a grid, and a thirdv electron.

a grid, means for connecting a source of-signalsv between said cathode and grid of said'first'elecf' tron discharge device, means' fory connecting "the,

the grid of said secondelectrondischargejdee` 40' vice, means for ,connecting said first condenserin circuit between said anode and said cathode'v of saidsecond electrondischarge device, means, fo'r'j connectingr thelc'athode of'said second, el tron dischargedevice to theglid oifsaid-,thin electron 'discharge device, and means frmconsaid yanode and said cathode of said third Velec- ,y tron discharge device whereby said condensers arey charged substantially simultaneously upon the appearance ofv a signal in the input circuit of saidrst electron discharge device, and means including a constant current device for discharge' ing saidycondensers substantially linearly with respect to time between signals applied to the 55 15. In combination, a pair of substantially equal condensers, a terminal of each of which is connected to a point ofthe same fixed potential, and means for substantially simultaneously charging said condensers, saidrmeans comprising a gas-lled grid-controlled electron discharge def vice having an input and an output circuit, means for connecting a source of signals to the inputr circuit of said gas-filled discharge device, a 65 third condenser, means yfor charging said third Asaid resistance in the input circuit of `said high vacuum electron discharge device, a second high vacuum electron discharge device, means for connectingl the output? circuit of said rstelec- 75 e `necting the second condenser in circuit between tron discharge, device to the input circuit o said second electron discharge device, means for connecting said first condenser in the output circuit of said second electron discharge device, a, third electron discharge device having input and output, circuits, means for connecting the output circuit of said second electron discharge device to the input circuit of said third electron discharge device, and means for connecting said second condenser in the outp-ut circuit of said third electron discharge device.

16. In combination, a pair of substantially equal condensers, a terminal of each of Which is connected to a point of the same xed potential, Vand means for substantially simultaneously charging said condensers, said means comprising a gas-iilled grid-controlled electron discharge device having an input and an output circuit, means for connecting a source ofsignals. to the input circuit of said gas-filled discharge device, a third condenser, means for charging said third condenser, a resistance, means including said gas-filled electron discharge device for discharging said third condenser through said resistance, a high vacuum electron discharge device having an input andan output circuit, means for connecting said resistance in the input circuit of said high vacuum electron discharge device, a second high vacuum electron discharge device, means for connecting the output circuit oi4 said rst electron discharge device to the input circuit of said second electron discharge device, means for connecting saidrst condenser inthe output circuit of said second electron discharge device, a thirdV electron discharge device having input and output circuits, means for connecting the output circuit of' said second` elec? tron discharge device to the input circuit of said third'electron discharge device, means for connecting said second condenser in the output circuit of' said third electronv discharge device whereby said condensers are charged substantially simultaneously upon the appearance of a signal in the input circuit' of said gas-filled electron, discharge device, and means including a `constant current device for discharging said pair o f condensers substantially linearly with., respect to time between,'signalsappliedi t o the,

input circuit of said` gas-filled electron dischargeA device.

charging said condensers, said means comprising;

a source of pulses, a first electron discharge cievice having an anode,l a` cathode and a, grid meanslr for connecting the grid of, said nrstelec-Y tron discharge device to said source of pulses means for connectingI said rst condenser in, the anode-cathode circuit of said iirstelectron,

discharge device, a second electron discharge device having an anode, ac athode anda gridmeans for connecting the grid of saidsecond electron discharge device to the'ca'thode of said ilst` electron discharge device, and means for connectingy said second condenser in the anode-cathodecir-` cuit of said second electron discharge device.

18. In combination, arst condenser, a, secondV condenser, means for connecting a termi#- nal of each of said first and second condensers to the same point of fixed potentiahmeans f or chargingvsaid condensers, said meanscomp-rising a source of pulses, a first electron discharge de,- vice having an anode, a cathode and a grid; means for connecting the grid of said iirst' electron discharge device to said' source ofA pulses, means for connecting saidliirst condenser inthe anode-cathode circuit of' saidrst electro-ndischarge device, a second electron dischargevv def, viceV having an anode, a cathode and a grid,

means for connecting the grid of said second', electron discharge device to the cathode of saidj first elec-tron' discharge device, and means for connecting said second condenser in the anode,- cathode circuit of said second electron discharge device, and means including a constant currentf device for discharging said condenserssubstantially linearly with respect to time between pulses applied to the grid of said iirst electron discharge-l 

